This invention relates to a processing apparatus for removing a remaining processing agent from the edge portion of a substrate, such as an LCD substrate or a semiconductor wafer.
In the manufacture of liquid-crystal displays (LCDs) or semiconductors, lithography processing is carried out to form a resist film pattern on the top surface of an LCD substrate or a semiconductor wafer. The lithography processing includes various processing steps, including the washing of a substrate, the drying of the substrate, the application of resist to the surface of the substrate, the exposure of a photosensitive film, and development. For example, after a substrate has been washed, it is subjected to an adhesion process. After the resulting substrate has been cooled, photoresist, a type of resist, is applied to the substrate to form a photosensitive film on the surface of the substrate. After the substrate has been heated in a baking process, an exposure machine or optical stepper exposes the photosensitive film to form a specific pattern. After a developer has been applied to the exposed surface of the substrate and the pattern has been developed, the developer is rinsed in a rinse solution, which completes the developing process.
In such a lithography process, the process of applying resist uses a spin coating method or a spray method. When resist is applied by these methods, the film thickness immediately after the application is uniform. After the rotation has been stopped and centrifugal force has not been exerted, or as time passes, the effect of surface tension permits the resist to get thicker at the substrate peripheral portion. There may be a case where the resist shaken off by rotation will fly to the back of the substrate and stick to unexpected portions. Such a non-uniform film formed at the periphery of the substrate and the resist stuck to the back contribute to the generation of particles in subsequent processes, including the process of transporting the substrate. The resist stuck to the back of the substrate also contribute to soiling the substrate transporting machine.
To avoid these problems in the prior art, the process of removing the unnecessary resist stuck to the periphery and back of the substrate is carried out after resist has been applied to the surface of the substrate. The removal process is achieved by moving a nozzle along the periphery of the substrate, supplying a resist solvent from the nozzle, and simultaneously sucking the dissolved resist by the supply of the solvent, thereby removing the resist.
Since generally used solvents are highly volatile, removal of the unnecessary resist using a solvent causes the fear that the solvent will evaporate into the surrounding atmosphere and worsen the environment. There is a possibility that the solvent evaporated in the surrounding atmosphere will have an adverse effect on the substrate and related things in the remaining processes. With a processing system for subjecting a substrate to a lithography process, to prevent such a solvent vapor from leaking out into the surrounding atmosphere, a fan filter unit is provided in the upper part of the apparatus to form a down flow. Just providing such a fan filter unit cannot prevent the solvent vapor completely from leaking out.